Wireless communication devices have become essential for modern day living. These devices provide many communication and data processing functions. However, there are various studies alleging that radio waves from the devices may be harmful. A recent study addressing this issue was reported in Friedman, J., Kraus, S., Hauptman, Y., Schiff, Y. and Seger, R., “Mechanism of short-term ERK activation by electromagnetic fields at mobile phone frequencies, Biochem. J., Vol. 5, 2007, pages 559-568.
A standard metric of radiation is the specific absorption rate (SAR). SAR is a measure of the rate at which energy is absorbed by the body when exposed to a radio frequency electromagnetic field, and is defined as the power absorbed per mass of body tissue with units of watts per kilogram. There is much advisory literature and product documentation about SAR levels of mobile phones.
U.S. Pat. No. 6,195,562 to Pirhonen et al. describes restricting maximum transmitted power of a mobile communication device, based on mode of usage of the device.
U.S. Pat. No. 7,146,139 to Nevermann describes use of a sensor for reducing the SAR of a mobile communication device. The sensor detects when the mobile communication device is in proximity to a body, such as a human body, and reduces the average power of the radio frequency electromagnetic energy radiated by the device accordingly.
U.S. Pat. No. 7,499,722 to McDowell et al. describes proximity regulation with a mobile communication device. Proximity regulation uses a location sensor to determine proximity of the mobile communication device to a user based on a mode of operation of the device. A power governor is coupled to the location sensor to adjust a power level of the device, based on the proximity.
U.S. Publication No. 2005/0124305 A1 to Stichelbout describes adjusting transmission power of a mobile communication device in response to proximity of the device to a person, whereby the transmission power of the device remains in the same power class as prior to adjusting the transmission power.
International Publication WO 2009/040796 A1 to Luzzatto describes a telecommunications policy that reduces SAR by disabling a sound input and/or output channels of a mobile communication device.
International Publication WO 2009/101618 A1 to Luzzatto describes a headset that measures distance between a mobile communication device and the headset, and notifies the user so as to maintain a safe radiation range.
Most of the prior art approaches the problem of limiting radiation by adjusting power level of a radiating device. This approach has two drawbacks; namely, it is intrusive to the user, and it is not favored by mobile carriers due to connectivity issues.